My mother in law got us what I call a leash, for our 4 year old. It has a vest which looks like a backpack and has a monkey on it. My son loves it but my wife is reluctant to use it. We have gone to a theme park this year and I found it invaluable to keep up with him. I sure didn't want him to squirm out of my hand when we were both sweaty and go running down the street. She sort of got annoyed at me for using it but I would rather be safe than sorry. What do you think about these things?